Radix Puerariae is the underground root of Pueraria, i.e. a perennial leguminous plant. As first recorded in Shennong's Chinese Materia Medice, Radix Puerariae was listed as a medium grade drug. Because of being rich in starch and isoflavones, Radix Puerariae is listed as both food and medicine by the Ministry of Health. There are more than 30 types of Pueraria in the world, which are distributed in China, Japan and southeast Asia. Among others, China, owning about 9 types of Pueraria and 2 mutations thereof, is the distribution center. Pueraria resources, including P. Lobata(will)Ohwi, P. Thomsoni Berth, P. edulis Pamp, P. Omeiensis Wang, and P. peduncularis Crah. ex Benth, etc. are all over the whole country, wherein P. Lobata(will)Ohwi and P. Thomsoni Berth are the most common Pueraiaee and have the highest resource amount. From a preliminary calculation, the growth area of Pueraria (including wild and cultivated) is approximately 400,000 hm2, and the annual resource amount is over 1,500,000 tons. Radix Puerariae has become the focus of economic crop development project in many places in China, so its planting area is huge. The main components of Radix Puerariae are starch, cellulose, protein and Radix Puerariae isoflavones, and a small amount of fat, pectin, tannin and alkaloid, etc. are also contained. It is reported that the dry Radix Puerariae has 50-60% of starch, 9-15% of cellulose, 5-8% of raw protein and 3-5% of isoflavones. However, the fresh Radix Puerariae contains about 50-60% of water, and 18.5-27.5% of starch. Therefore, when considering extracting and utilizing Radix Puerariae flavones, i.e. the active pharmaceutical ingredient of Radix Puerariae, Radix Puerariae, as a starch-type energy source plant, may also be fermented to produce ethanol.
It has been reported that the extraction methods of Radix Puerariae flavonoids are water extraction method, alcohol extraction method, water extraction and alcohol precipitation method, alcohol extraction and water precipitation method, and the like. In 1970s, Radix Puerariae flavonoids were prepared by the Chinese Academy of Medical Sciences by means of a basic lead acetate precipitation method, i.e. a classic alcoholization method of flavones. Nevertheless, such method commonly causes heavy metal contamination, so it is not suitable to be used in pharmaceutical industry. Although the components of Radix Puerariae are very complicated, the pretreatment of Radix Puerariae for the extraction of flavones normally is only a simple mechanical crush.
The current application of Radix Puerariae's active ingredients is most likely in the processes for extracting Radix Puerariae starch and flavones, respectively. However, since Radix Puerariae contains a large amount of fibers, the mechanical crush requires a lot of energy, which leads to a complicated and incompleted starch extraction process and causes a waste of raw material. If the extracted Radix Puerariae starch is utilized to produce ethanol according to the process for producing ethanol from food-type starch, i.e. a process of steam boiling at a high or low temperature—gelatinizing—liquefying—saccharifying—liquid fermenting—primary distilling, wherein the energy depleted for steam boiling the raw material amounts to 30-40% of the total energy needed for the production of ethanol. Furthermore, such a process results in a great amount of highly concentrated organic waste water, which is not only likely to pollute the environment but also difficult to be used to extract Radix Puerariae flavones. Thus, for reasonably utilizing Radix Puerariae resources, it is required to make use of the characteristics of Radix Puerariae and develop a process suitable for co-producing ethanol and Radix Puerariae flavones as well as utilizing Radix Puerariae fibers from Radix Puerariae, thereby accomplishing a comprehensive utilization of Radix Puerariae resources.